I got this done on Overdrive 1 in Backlot Battle with a boosting buddy.
Assuming Player 1 (P1) needs the achievement and Player 2 (P2) is helping.
Get both players to turn around as soon as the time starts and head the wrong way round the track until you get to the 2 corridors/alleys.
P1 waits at the top by the lorry that you can drive under. P2 keeps going up and down the two corridors keeping their string alive.
I would say try to aim for a 100x multiplyer - that way you are guaranteed that it will be 100,000 points or more.
Then with P2's string still alive. P1 needs to crash into the back of P2 to steal their string.
I finished the 3 laps just to be sure, but you might still get it if you 'fail' the battle.